The fire appeared to have started in an area where the furnace comes through the roof, Finn said.

Boston Mayor Marty Walsh called the blaze "the biggest fire that I've seen as mayor of the city."

Boston EMS tweeted Friday night that two people had been sent to local hospitals with minor injuries. One police officer who was helping to evacuate residents was treated for smoke inhalation, Finn said.

Thick, billowing plumes of smoke and large flames continued into the night, hours after the fire broke out around 3 p.m. The fire went to nine alarms by 6:15 p.m.

City officials used the reverse 911 system to evacuate residents in the Orient Heights section of the city. A shelter has been set up for those forced to evacuate their homes.

Grateful for the incredible bravery and hard work of our first responders battling the fire in East Boston.

We will continue to support the Orient Heights neighborhood and all those affected, and we urge residents to respect the guidance & direction of public safety officials.

Finn said the fire extended throughout all of the buildings. "A multitude of buildings" that were connected -- some were old, some were new -- are a total loss, he said.

"The problem is it's an awfully big fire, for sure. Our issue is water. We need pumps," Finn said.

A concern has been chemicals from the building seeping into the air, Finn said. The chemicals are used to lacquer the caskets, he said.

"They’re less toxic than the real bad stuff. So they are toxic. They are. We've been monitoring and it’s in a good acceptable range," Finn said.

The MBTA tweeted soon after that the fire department requested the Blue Line suspend its service between Orient Heights and Wonderland.

Shuttle buses are replacing Blue Line service in both directions.

Residents in the Orient Heights neighborhood were ordered to evacuate due to heavy smoke conditions. Reverse 911 calls went out to those who need to evacuate. They were told to go to Curtis Guild Elementary School at 195 Leyden St.

Boston Fire says people should avoid the area.

"We’re going to be here throughout the evening as you can see. It’s just a very difficult fire to fight right now because of access," Finn said.